I got curious about this, so we tested it. Based on our testing, if your opponent has Rat Trap, and Masked Contender is the second card you play in a turn (which is the only way that the Secret it "plays" would activate the trap), it does not activate Rat Trap. You'd still need to play a third card to activate your opponent's Rat Trap.

Can you recall the circumstances under which you activated Rat Trap with Masked Contender's Secret? Maybe there was something else going on.

Edit: All that aside, we get why there might be some confusion about the text on this card.

I know there was a bug where Spellbender redirecting a spell caused it to double count, but I can't find any reports about Masked Contender causing it. Sure this isn't some Mendela Effect brought on by a different bug?

Edit: All that aside, we get why there might be some confusion about the text on this card.

Eventually, Magic came up with strict templating guidelines for cards and applied them to all the older cards as well. Someone has to realize that we’ve been complaining about a lack of consistent templating on cards for years.

On top of that, Magic's rules and card templating are so good that they just type the card text into their importing tools for Arena and MTGO, and the tool is able to create the background programming for +95% of the cards in any set.

Any considerations for adding “players/heroes” into secret keeper’s description as the one casting? Not a large change and makes it more intuitive with all the minions now that are capable of casting spells.

Now that minions can cast spells (and have been able to for like 2 years), it'd make more sense to differentiate between "cast" and "play" the same way they do with minions being "summoned" or "played". "Play" always means user plays the spell from the hand, "cast" can mean either.

This was quite a while ago, back during the first month when Rastikhan's Rumble came out. I'd used Secret Plan to acquire Rat Trap and placed it down, as I didn't main it in my Spell Hunter deck.

My opponent already had a Secret out, then used Coin and played Masked Contender, placing down a Secret. This activated my Rat Trap, which surprised the heck out of me, as I wasn't expecting it at all.

I'm sorry I don't have more to provide! It's the only time I'd been in that situation, as I don't play too often. Again, thanks for responding, and let me know if you need anything else.